The Eighth Sin
by The Castle in the Clouds
Summary: Everyone thought that with the death of Father, peace could once again be found. But a sinister and dangerous threat lies below central, a fail safe that Father put in place incase he would fail. An eighth Homunculi, the most powerful and personal of all the sins he had purged himself of: Vanity. The Homunculi with the backwards Ouroboros.
1. Chapter 1

_Hello everyone and welcome to my story! Please review and let me know what you think, the feedback really keeps me going! If you have any questions just ask and I'll be more than happy to help. Other than that I sincerely hope you enjoy!_

 _ **Summary:**_ Everyone thought that with the death of Father, peace could once again be found. But a sinister and dangerous threat lies below central, a fail safe that Father put in place incase he would fail. An eighth Homunculi, the most powerful and personal of all the sins he had purged himself of: Vanity. The Homunculi with the backwards Ouroboros.

 _ **Disclaimer:**_ I do not own Fullmetal Alchemist or any of the characters. I can't just let them sit idle after the promise day, so I decided to throw another challenge their way :)

* * *

 _ **The Eighth Sin: A Story Written by The Castle in the Clouds**_

* * *

 _ **~Chapter 1~**_

Central was as busy as ever. The streets were consumed by cars and the sidewalks flooded by footsteps. People went about their business as usual, finally returning to normal life after the assault on Central. The military was regaining it's support from civilians as it tried to rebuild its reputation, and at the head of that endeavor was Roy Mustang. After the death of King Bradley, Grumman was promoted to Fuhrer and Roy mustang was only one rank below: General. Even though he never made it to Fuhrer (yet) Mustang had much more influence and say than when he was Colonel. He worked side by side with Scar to repay the Ishvalans and give them back their homeland of Ishval. Along with that he put in a good word for his most trusted soldiers, but all of them said that preferred to remain where they were after all that had happened. They figured that until the military was back on track it was best _not_ to get too involved, everyone except Riza Hawkeye. She swore to be at his side no matter what, and with that gladly took the new rank of Lieutenant General, only one rank below Roy. As they worked side by side to rebuild the military into what they knew it could be, something sinister was lurking about under Central. Something that was about to emerge from the depths to reopen old wounds and wage war on Amestris once more. A fail safe that Father had put in place, the most powerful and personal sin that he held...

Vanity.

* * *

Little clanks and pings could be heard as metal expanded and retracted and water dribbled from above. The underneath of Central was a cold and dark place, full of bad memories and blood. It was a place that no one dared to enter again, a place void of light. Metal tubes ran everywhere and sewers paved water ways full of crap. But amongst the inhospitable and menacing place below Central lied a Homunculi, one last sin that Father had purged himself of. A sin that he never told any of his children about, something he set in place as a fail safe incase everything went wrong.

"Well well, looks like he did need me after all." Spoke a woman in front a mirror. She had long golden hair that fell over her shoulders, and cold bitter eyes that shone silver. She wore skin tight black leather pants and a jet black hoodie with a _backwards_ ouroboros tattoo stamped on the back of her neck. It front of the mirror she stood, and in front if it should would have remained if it weren't for the task she was given. If she was to wake up, to be able to look at herself again, it would have meant that Father and the rest of her siblings were killed. So why did she need to serve a man who was dead? Well, she was vain and full of herself, valuing herself above all else in the world. But she wasn't prideful, she would do _anything_ that would get her praise or attention. Good or bad.

She was Vanity the Vainglorious.

"It seems I have work to do..." She stood in front of the mirror a while longer as she admired her vast beauty. She played with her hair and turned side to side as she looked over herself, a grin sweeping over her face.

Vanity left the mirror with a sigh as she walked into the main room where Father's chair laid empty. She smiled and walked up to it, running her fingers over the cold steel armrests before sitting down and crossing her legs.

"So the old man failed. That's why he made me, he _knew_ I couldn't fail. He knew I was strong where he was weak, and he was right." She gave a small but self glorified laugh as she relished sitting in the coveted chair.

"I really am something else aren't I?"

Cold and lonely silence hung over the room as she waited for a reply.

"This place sure is lively..."

Vanity got up and walked through the underneath of Central, strutting as if it was her palace. She would periodically run her hand across the frigid and barren walls as if to claim it for her own. She did this as she made her way to the staircase that lead up and out of that decollate place. Every footstep echoed though the empty halls as she climbed each step, making it to the gate as she opened it with a creak. Stepping out into the ally and into fresh air she took a deep breath and placed her hands on her hips as the gate slowly swung closed behind her.

"Ahh, Central. I though I'd _never_ get to see this place."

She smiled and walked out of the ally and into the busy street of Central, blending in amongst the civilians like a wolf in sheep's clothing...

* * *

"Edward!" Winry scolded as she popped her head into his room, his suitcase lay open on his bed with clothes all over the floor. Ed gave a surprised wince as her voice rocked his eardrums.

"You're not ready yet?"

Ed turned around in his desk chair as he gave Winry a weak smile. "I'm almost done! Then I'll get packed up I promise." He turned to finish scribbling on the piece of paper that sat on his desk.

"Your train is going to leave in fifteen minutes and your not even packed!"

"Nng!" Ed got up in his chair and stood as he desperately tried to finish writing whatever he was writing.

 _Damnit Winry, I'm almost done with..._

He sighed and crumpled the paper in his fist as he tossed it in the trashcan that sat next to him, desperate not to miss his train.

 _Ill just ask her at the station..._

Ed got up and began collecting up the scattered clothes on his floor and bed as he piled them into the suitcase. He was so disorganized, and Winry couldn't figure out why he was also unpunctual.

"What were you even writing anyway?"

Ed froze for a second before continuing to get his suit case in order, trying not to blush too bad. "I-it was nothing, really."

Winry sighed and rolled her eyes as she watched him jump from his desk to his suit case and back again. Even though he was still, well, Ed. She couldn't help smiling at him.

"Well it must have been important enough to make you late for your big day..."

Edward gave a sigh as he closed the lid and snapped it shut, picking it up by the handle and letting it dangle at his side. He swapped out his old Flamel red coat for a brown one since he wasn't an alchemist anymore. He stood and smiled at Winry as she looked him over.

"Well, at least you look a _little_ prepared for your journey West..." Winry smiled and stepped out of the doorway and let Ed follow her downstairs. As he followed he tried not to bang the case against the walls, the wrath of Pinako was not to be reckoned with.

"You going to be okay while I'm gone?" Edward asked. Winry looked at him for a moment, surprised at his blatant concern. Usually she had to decipher his feelings and sift thought them, but it was kind of nice to see him finally ask straight forward.

"Yeah, I'll be alright. I've got plenty to keep me busy, and maybe I'll head to Central to visit Ms. Hughes."

Ed nodded and smiled as he turned to reach for the door, they had to walk briskly if they hoped to catch the train in time. But as the door swung open the telephone went off, causing them both too pause.

RING! RING!

"Should we get that?" Ed questioned as he looked to Winry.

RING! RING!

"Nah, you need to get going... I can call them back, it'll be ok."

Ed nodded and opened the door again, this time pausing in the doorway.

"Ed, what's wrong?"

RING! RING!

"Maybe you _should_ get that?"

Winry sighed and turned to pick it up. Ed was so unpredictable. First he stresses and nags about getting everything ready for today, then he's late because of writing some stupid notes or something, and _now_ he's going to be late over some phone call. It didn't make sense, but then again Edward never did.

"Hello, this is the Rockbell Auto Shop how may I help-,"

Winry turned around and looked to Ed. "Yes, he's right here." She held the phone out, gesturing that it was for him. Ed furled his brow in confusion as he walked over, letting the door shut on its own. He snagged the phone from Winry to find out who it was.

"Yeah, this is Edward... Mustang?... Yeah?" He looked at Winry as he shrugged his shoulders, unable to give her a clear answer. "No, I was heading out now why?... Al? Yeah he's already heading East... Because we were going to learn about-," Ed cut off his sentence and rubbed his forehead with his digits. "Look what's wrong?"

Winry shifted her weight onto one leg as she stood and wondered what was so important that Mustang would be calling.

"What?!"

Winry's eyes widened as she observed Ed's body language. Apparently it wasn't good news. Edward's hand began to tremble as the phone shook a bit, he leaned onto the counter and balled up his fists.

"Your sure? I mean your positive that's what it is?... Yeah I'll be there." Ed nodded as he listened, his hand trembling as he finished his conversation and hung up the phone.

"Edward what's wrong? What happened?"

Ed looked up to her with anger. "Change of plans, I'm heading to Central."

Winry furled her brow and shook her head. What was so bad that Ed would abandon his journey? What did Mustang say? Edward dropped his suitcase and headed for the door, opening it and stepping onto the porch.

"Ed wait! What's going on? You left your suitcase!"

He paused and pivoted to look at her. "Scar was murdered and the Ishvalan's are on the brink of starting another war..."

Winry's hand instinctively covered her mouth as she fought back tears. How could someone kill Scar? From what she knew of him and what she's seen, he is an alert killing machine that not even Ed could best. And with his death came even more blood between Amestrians and Ishvalans, the hope of their homeland seemed grim.

"And to make it even worse, an ouroboros was drawn in blood..."

* * *

Roy hung up the phone and placed his elbows on the desk, resting his chin on his hands. Hawkeye stood at the corner of his and observed his body language. She agreed that this was an unfortunate and strange case, but she also had to admit that there _were_ many people who would have been pissed at the Ishvalan return treaty. But it was the ouroboros drawn in blood that made shivers run down her spine. There were only a handful of people who knew what that meant, and amongst all of them _none_ of them would have even thought about killing Scar. But could it really be?

"Sir." Riza spoke up. "Are you ok?"

Roy kept staring at the doorway in front of him, neglecting to answer her question.

"Sir, the ouroboros could mean anything."

Mustang lifted his head to look at her. He was obviously shocked and upset about the resent events. He had _finally_ gotten into a position to return the Ishvalan's homeland back to them, to be able to make up for his sins in the war. He was going to get this military straight and bring it to the potential he always saw. Now it seemed like all his endeavors and all his hard work went down the drain.

"Lieutenant General Hawkeye, send a message to Alphonse. We'll want him on this case too, we need all the help we can get and those brothers know more about the homunculi than anyone else. I believe Alphonse is heading to Xing, and there is a small town called Youswell on the border where he should be spending the night before crossing the desert. I believe we have enough time to get the message there before we loose him across the border."

Riza gave a salute as she clicked her boots together. "Yes sir."

"And one more thing. Make sure the apartment is cleaned up incase we have guests, we don't want to be unprepared." He gave a specific look that Riza knew all to well. She eyed him and gave a nod to show that she understood his message before turning and carrying out the order, leaving Roy to ponder.

Mustang sighed and reached into one of his desk drawers, pulling out his chess board.

 _If this is a game then lets play..._

He unfolded the board and pulled out all the black pieces, setting them up in their respected positions and studied them. After, he swiveled the board until the empty side was in front of him. Looking at the empty side he pulled out four pieces. The King, The Queen, The Knight, and The Rook.

 _I have no idea whose behind this or who the players are, It may be a full board or only a few pieces... But all I need is my three. My Queen, Riza. My Knight, Edward, and my Rook, Alphonse... If we play this right we won't need to get anyone else involved or put anyone else in danger._

Roy fingered the pieces as his picked up the King, flipping it over and over in his hand as he studied it. Who could have done this? And Why? I mean he could understand why, hell he even expected an attack on someone aiding in the Ishvalan return. He was confident he could quell an uprising, and he was sure he could still keep the treaty active. But the ouroboros made him wonder, made him sweat. Why the hell was it drawn? Who even _knew_ about it? Then his mind wandered to a few years ago when they were fighting the homunculi. How could he ever forget how slippery and well organized those bastards were? Sure they were able to win in the end, but it took every ounce of strength and strategy that they, that he, could muster. And on top of that all of the Homunculi were dead, all except Pride. But he was barley two years old by now, surely he didn't remember anything yet? And its not like there was another one, an eighth one?

I mean... that would be ridiculous.


	2. Chapter 2

_Hello! I hope you enjoy the next chapter! I just wanted to let you know that my updating will be random due to writing, editing, and making sure there are no grammar errors. So it may take a few days or a week, I cant really say. Whelp! Hope you enjoy and stay tuned for chapter 3!_

* * *

 _ **Chapter 2**_

* * *

Ducking under the yellow tape, Mustang showed Ed the way to the scene. Scar had been murdered in one of the bedrooms while he was asleep, and no one could imagine someone quiet enough to pull that off. His body had been removed from the crime scene by now, but the blood and the ouroboros still remained.

"Whoever pulled this off knew what they were doing," Mustang informed. "They simultaneously stabbed his heart and throat to ensure a quick and quiet death."

As they entered the bedroom the stench of blood tempted Edward to wear his lunch. Luckily a quick hand over his nose solved the problem.

"But if they stabbed him in the heart, then why the throat? It seems like overkill to me."

Roy pointed to the ouroboros on the headboard. It was _definitely_ that same accursed symbol that all the homunculi bore - except this one was backwards.

Ed observed the entire scene as his eyes shifted back to the ouroboros. "So that's it, huh? That's... weird," he mused quietly.

Mustang furrowed his brow as he glanced from Ed to the symbol. "What is?"

Edward walked up, trying not to disturb anything that could help find this asshole and observed it up close.

"Yeah... this was drawn backwards."

Roy followed and looked at it even closer, realizing that Edward was right. The dragon was going in the wrong direction.

"Which means that it may _not_ have been a homunculus after all. Just someone who understands the lore enough to make it _look_ like a homunculus did it."

Ed stepped back and looked at Roy. "However, with all the weird shit that we've encountered... I wouldn't rule out the fact that it could still be one of them."

Mustang couldn't help but smile. Ed had grown _so_ much since he first met him in that wheelchair. He had gotten a lot taller and matured way more than he ever thought he would. It felt like he wasn't a kid anymore, but now an adult who was working alongside him.

Roy folded his arms and grinned. "If I didn't know any better, Fullmetal, I would say that you were a detective or a part of the military police."

Ed smiled back. "And If I didn't know any better I'd say that you needed me to help you find a lead."

They both eyed each other with a grin. They had been through thick and thin together, through hell and even worse. But it felt like they were partners now, like they could work side by side in a more professional way.

"So how did the killer get in anyway?" Edward inquired.

Mustang pointed to the window. "The door was locked from the inside but the windows weren't. I suspect that the killer climbed through, but I have my doubts."

Ed walked over to the ajar window and opened it further, sticking his head out and looking down with wide eyes.

"There's no way someone could climb all the way up here, there's no footing or ledges for them to climb," he stated. "Plus, if they _did_ end up coming through here, its a hell of a drop down. They would of at least broken their legs...,"

Roy nodded as he joined him. "Yeah, that's why I said I have my doubts. It makes sense now that someone could have staged it to look like a homunculus was responsible, but how they got in or out is unexplainable. And I can't shake this strange feeling that nothing is as it seems, and the last time I felt that was-,"

"Hughes' death...," Edward finished solemnly.

The two finished examining the crime scene before Roy turned and left, Ed not far behind. They walked through the halls of Central Headquarters, officers stopping and saluting Roy as he passed.

"So, you a big wig now or something?" Ed asked.

A smile graced Roy's lips as he kept leading them to his office. "Yeah, something like that," he answered.

The duo kept walking as they turned corners and climbed flights of stairs; it had been a while since Ed walked though Central HQ, and the place seemed more orderly but less tense. It was as if even the military felt a sense of peace - until Scar's murder, that is. Eventually they ended up reaching Mustang's new office, entering and closing the door behind them.

"Sir!" saluted Hawkeye as they entered the room. Roy waved a hand, causing Riza to relax and lower her hand. "And welcome Edward."

Ed smiled. "Oh, hello lieutenant."

Roy took a seat at his desk and grinned. "Careful Fullmetal, she's your superior now." he teased.

Ed looked over to Riza curiously. Roy was right - she had a straighter stance and a more dignified look to her. And the fact that she was his superior (even though he was no longer with the state) meant she ranked above Major.

"Congratulations. So what were you promoted to?"

Riza smiled. "Lieutenant General."

Ed's eyes widened with shock, his surprise obvious. "Damn, isn't that one rank below...,"

"General, yes," Roy finished, his tone suggesting that he held that title. Ed looked to him and chuckled. He got so used to calling him Colonel and Colonel Bastard, now he was going to have to adjust it. He knew that Roy wanted to climb the ranks, but to see him actually holding the title was something else.

"So you made it?" Ed confirmed.

Mustang leaned back in his chair and crossed his legs. "No, not until I'm Fuhrer. This position is just temporary - I still have my eye on bigger prizes," he explained.

Edward sat down with a smirk. "So you're still going for it, huh?"

"Yes, but I think we have more important things to discuss than my rank and military ambitions."

Ed and Riza both agreed. The three of them _had_ to put the pieces together so that no one else was involved. Plus, once they got their theory they could add Alphonse into the mix with his fresh set of eyes. Hopefully... hopefully they would all agree on a lead to follow. Or at least come up with one.

"So let me get this straight," Ed began. "Scar was asleep. And someone with enough skill to climb a _flat_ wall came through the window quiet enough to sneak past Scar? Then they killed him quiet and efficient enough to have time to draw that damn ouroboros?"

Riza and Roy glanced at each other in silence. When Edward put it that way, it seemed impossible to attempt let alone succeed.

"Yeah, and to top if off there were armed guards outside his door. I didn't want to take a chance at leaving him alone," Mustang added, giving a defeated chuckle at how well it ended up helping.

"Yes, the General and I both agreed that protection was necessary since there were bound to be people that were angry with the situation. The military did such a good job making the Ishvalans look like the bad guys in the war of extermination that we suspected an attack on Scar or anyone helping in the return treaty."

Ed nodded as he ran the information through his head. It was like adding apples and oranges; it just didn't work.

"Can you think of anyone who stands out? Anyone that comes to mind when you think of an assassination?" he asked.

Roy and Riza though for a moment before shaking their heads. No one really stood out, and no one had made a public disagreement yet. In fact, they were actually surprised at how little resistance they were getting.

"Ok then, how about the ouroboros? _Someone_ had to know what it meant. Someone who wanted to kill Scar _and_ knew the meaning. If we can link the two to someone then we'll have a solid lead."

Roy nodded, plunging deep into thought. Ed was right, if they could connect the two then they would have their lead. But the problem was that the only people who know about the ouroboros were Mustang's most trusted team members. And he knew that none of them would even imagine the idea, let alone carry it out. And no matter how much he admired them, he had to admit that they all lacked the skill to pull it off.

"What if it really _was_ a homunculus that did it? I mean, I remember when I kept unloading rounds into Gluttony's face and he barley flinched. If it was one of them it would explain both the symbol _and_ the unnatural nature of the crime," Riza asked.

Both Ed and Roy gave a deep sigh.

"Yeah, that crossed my mind too," Ed admitted. "It _would_ explain everything. The only problem is that the only one left is Pride, and he's barley two years old. Unless... unless that bearded bastard created an eighth one. Knowing him I wouldn't rule it out."

"Yes, it's definitely an option," Mustang agreed. "Although I wouldn't rule out human suspects either...,"

* * *

The atmosphere was wonderful. The people of Youswell were happier and merrier than ever. Alphonse had made it to the border of Amestris, deciding to stay the night to get one last rest before the arduous journey ahead. Upon arriving he was happy to see how well they were doing. The mines were their home, and a home it had become.

"Well hello there! Another visitor!" pointed out one of the residents. "The last tourist we had was from Xing; saved our mine she did!"

Al smiled and waved, people now starting to crowd around and offer invites and welcomes. He tried to explain that he was the same suit of armor from all those years ago, but he couldn't even get in a few words. Al was eventually led to the newly built and improved in Inn, where he was sat down and offered food and drink.

"So! What brings a youngster like you to our humble mines?"

Al took a sip of hot coffee, setting it back down while trying not to make a contorted and sour face. It was black, and he was still getting used to bitter and sweet tastes.

"Well, actually I've been here before-,"

"Oh really? Well I sure don't remember you!"

The towns people were all gathered around the table that Alphonse was sitting at. Every time a tourist would come they would treat him/her to good food and drink because every tourist they've had ended up saving their lives or their home.

"Yeah, I'm Alphonse. Remember?"

The Inn keeper scratched at his throat as he tried to recall the name. "No, can't say I do, although the voice sounds familiar. Lets see... We just had a Xing girl pass through a couple years ago... She saved our mines with some type of alchemy. Oh! And I cant forget that state alchemist Edward Elric! Believe it or not he conned the son of a bitch that owned this town and gave the deed to us! Yeah, him and some suit of armor."

Al smiled as the fond memory. It really _was_ a long time ago. "That suit of armor. That was me, Alphonse Elric."

The inn keeper looked at him funny. "You mean _you_ were the one in that suit of armor?"

Al nodded with a smile as he folded his hands. "Yeah, and Ed is my older brother. People often got that confused due to our height difference at the time."

Halling gave a hearty laugh. The rest of the residence had begun occupying themselves with food, drink, conversation and dancing, leaving Al and Halling to themselves.

"Yeah I can't forget him, he sure was a pistol. But you? Damn, you've shrunk a lot!"

Al felt a twinge of anger. He wasn't _that_ short! If only they understood that the armor wasn't his actual body. That he was now had his _real_ body back and just got it healthy enough to travel.

"So what gave you that weird armor hobby anyway?"

Al took a deep breath. He wasn't easily angered like Ed, but it did seem a little rude to be talked to like that. _Especially_ when he helped give them their mines back. But before he could answer the Inn doors swung open, revealing a military officer.

"Does anyone know where I can find Alphonse Elric?"

The inn went quiet as the residents stopped their nightly festivals and glared at the man. Halling proceeded to stand up, still distrusting the military. After all they had been through it was hard not to remember those times when a uniform showed up.

"Why?"

The tall and muscular man smiled and stroked his mustache. "I have an important message for him."

Alphonse smiled and pushed through the crowd of people. "Major! It's good to see you!"

Alex Louis Armstrong smiled and stooped down to hug him, wrapping his arms around Al's body while almost crushing a few bones. "Alphonse! It's good to see you my boy!" he set him down, leaving poor Al to catch his breath.

"Its good to see you too, Major."

Halling glanced between the two with confusion. "So you became a dog of the military like your brother?"

Al turned and shook his head. "No," he replied, "the Major here is an old friend and one of the best men I know."

Alex smiled as pink sparkles orbited his head. "Why thank you Alphonse!"

Halling smiled and held his hands out to his sides. "Well, a friend of Alphonse is a friend of mine. Come! Enjoy some good food and good drink!"

Armstrong smiled but held up a hand. "I would love to but I came to deliver a message to Al. You are wanted at Central to help with a case. I can't discuss the details here, but I can tell you that your brother is already helping alongside General Mustang and Lieutenant General Hawkeye."

Al's eyes widened. If his brother was helping then so was he. But... what happened? He hadn't heard news of something bad enough to call them in. And besides, it's not like his brother was with the state anymore. Which means it's either more of a visit than a case, or... something terrible went down.

"Alright then, I'll come. If it's important enough to make brother stop his journey then I want to help out too. Besides, you guys might need my alchemy since Ed can't do it anymore."

Alex nodded as he invited Al to leave with him.

"Well Alphonse," Halling started. "I can tell you and your brother are good people and that you're really alchemists of the people. But there is definitely a story behind you two, so I hope one day you guys stop by again for a visit. I would sure love to hear it."

Al laughed inwardly and shook Halling's hand. "Yeah, it's more of a novel than a story," he said with a fond chuckle.

Halling laughed as he let his grip go. "Well either way, I'd like to hear it some day."

Al flashed a smile before turning to leave with the Major. "I look forward to it."


End file.
